VATICAN CITY — During a major summit of the Roman Catholic hierarchy that will end this weekend, a senior conservative bishop took the floor inside the Vatican’s assembly hall and promptly charged his liberal peers with doing the devil’s work.

The three-week gathering, known as a synod, has erupted into a theological slugfest over Pope Francis’s vision of a more-inclusive church, and it has displayed the most bitter and public infighting since the heady days of Catholic reform in the 1960s.

Archbishop Tomash Peta of Kazakhstan captured the magnitude of the divide, raising eyebrows — and a few incredulous laughs — as he decried some of the policy changes floated at the meeting as having the scent of “infernal smoke.”

It was just another day at a gathering that, more than any event since Francis began his papacy in 2013, has highlighted how the pontiff’s outreach to once-scorned Catholics has triggered a tug of war for the soul of the Catholic Church. More important, it underscored just how hard it may be for the pope to recast the church in his image.

The pushback by traditionalists has been so strong that the chances of fast changes on contentious family issues — whether to offer Communion to divorced and remarried Catholics or to craft more-welcoming language for gays and lesbians — have substantially dimmed, if not died.

As the synod’s end nears, there has been a last-ditch push to find common ground that could at least open the door to policy alterations. But some observers already are comparing Francis to President Obama — a man whose reformist agenda was bogged down by a conservative Congress.

“Francis has the same problem that Obama had,” said the Rev. Thomas J. Reese, a senior analyst for the National Catholic Reporter. “He promised the world, but Congress wouldn’t let him deliver. If nothing much comes of this synod, I think people will give the pope a pass and blame the bishops for stopping change.”

For Francis, the synod — the Vatican’s second in a year on issues related to the family — sets up perhaps the most important decision of his papacy.

The 270 senior church officials, from 122 countries, are scheduled to finish voting on a final document by Saturday. But Francis has the last say, with the power to accept the synod’s recommendations, go beyond them or withhold judgment to encourage further debate.

All of those avenues, though, carry risk.

Using his powers to go beyond the synod’s recommendations could rouse the wrath of conservatives, some of whom already are openly questioning the trajectory of his papacy. But if the final recommendation of the synod falls short of liberals’ hopes, ­rubber-stamping it or encouraging more debate could generate disappointment among Francis’s fans worldwide. They may begin to view him as a revolutionary only in gestures and words, not on substance.

Pope Francis reaffirms Catholic opposition to gay marriage as he opens a three-week gathering of bishops, but says the church has to show love and understanding towards all. (Reuters)

If he agrees fully with the synod’s recommendations, “there might be a collapse of his popularity in world public opinion, but there might also be an increase of his popularity among Catholics,” said Massimo Franco, author of “The Crisis of the Vatican Empire” and a columnist at the Italian daily Corriere della Sera.

Even by Vatican standards, the level of drama at the synod has been extraordinary.

As recently as Wednesday, the Vatican strenuously denied a report in the Italian media that Francis had a small brain tumor. That comes after another leak early this month revealed a letter sent to the pope and signed by 13 conservative cardinals — including Cardinal Timothy Dolan of New York — that seemed to question the pope’s handling of the synod process.

Adding to the drama, some of the 13 denied that they had signed it. Francis also recently warned the synod’s members not to be swayed by conspiracy theories, a move that some Vatican watchers considered a thinly veiled reference to the missive. To some senior Vatican officials, the letter appears close to open sedition.

“The widespread opinion I perceived among the fathers has been a sense of disgust,” Bishop Marcello Semeraro, one of the senior clerics who will draft the final synod document, told the Web site Vatican Insider.

But by telling bishops that nothing is off the table for discussion, Francis has broadened what can be examined — including his management style. Conservative bishops, though, think he has unleashed a free flow of ideas that have startled some traditionalists and provoked a sharp backlash.

Francis still has not openly stated if, when and how he would like to see church policies altered. But his calls for a more merciful and open church, his pastoral outreach toward divorced and gay Catholics, and his decision to allow wide-ranging discussion at the synod have inspired leading church liberals to press for change.

Of the many measures under debate here, two have emerged as the most polemic.

One is whether to grant divorced and remarried Catholics, who are committing adultery in the church’s view, access to Communion. The other is the question of whether to offer a warmer welcome to gays and lesbians, including cutting references to being gay as “intrinsically disordered” from church teachings.

The divide is not just a liberal-conservative split; it is also geographic, with prelates in Africa, for instance, denouncing the “Eurocentric” and “Western” fixation with issues such as gay rights.

Guinean Cardinal Robert Sarah linked the push for gay rights to abortion and Islamic extremism, comparing them all to what “Nazi-Fascism and Communism were in the 20thcentury.”

The vehemence of the backlash has shocked even some moderate conservatives, and it has suggested the rise of a tea-party-like faction of bishops within the hierarchy.

“Some of them are talking now like this is Armageddon,” Archbishop Mark Coleridge of Brisbane, Australia, said in an interview with The Washington Post.

“They see themselves as the sons of goodness and others as the sons of darkness and evil. I have been very surprised by this apocalyptic view of things at the synod. . . . This isn’t the way discussions are done,” he added.

The sniping has become surprisingly public — and personal. The powerful conservative Cardinal George Pell of Australia, for instance, suggested in an interview with the newspaper Le Figaro that an epic “battle” was taking shape in the church between the conservative theology of Benedict XVI and that of liberal German Cardinal Walter Kasper, who is considered a Francis ally and the architect of some of the most progressive measures fielded at the synod.

The Pell’s comment provoked a rare public rebuke this week from German Cardinal Reinhard Marx, who called out Pell by name at a Vatican news conference.

“In the synod, we are not in a battle. We are not Ratzinger versus Kasper,” Marx said, using Pope Benedict’s birth surname. “That is not okay.”

The plot thickened Thursday as an article appeared on a conservative Catholic Web site claiming to be from “a very wise, knowledgeable and highly influential cleric.” It is titled “The Failed Francis Pontificate.”

In it, the author, writing under the pen name Don Pio Pace and using insider terminology, argues that the divided church is now “intrinsically ungovernable” and decries this “strange synod” for being overwhelmingly focused on “adulterous couples and homosexual couples.”

Some also have denounced the general sense of chauvinism hanging over the debates, in which only male clerics have voting rights.

Maureen Kelleher, an American nun serving in one of the non-voting roles at the synod, told the National Catholic Reporter that there were “times that I have felt the condescension so heavy, you could cut it with a knife.”

Speaking of women in general, she added: “I see a high level of non-acceptance of us as holding up half the sky.”